Chimeric target molecules having a regulatable activity

ABSTRACT

The present invention relates to a chimeric target molecule having an activity which can be regulated or modulated by a binding molecule. The invention also relates to methods of using the chimeric target molecule to detect the presence and/or amount of a desired analyte in a sample. The analyte is a binding molecule, or a competitor of a binding molecule, which binding molecule, upon binding to the target molecule, alters the activity of the target molecule in a detectable way. In one aspect of the invention, a binding molecule binds to the chimeric molecule, inactivating it. An analyte in a test sample competes and/or displaces the binding molecule from the chimera, reactivating it. The reappearance of activity in the presence of the analyte indicates its existence in the test sample existence and amount. Another aspect of the invention relates to a binding molecule which regulates a chimeric target molecule and methods of producing it.

BACKGROUND OF THE INVENTION

The development of assays for measuring the presence and amount of desired substances is highly desirable for a variety of purposes, including for medical, veterinary, research, and environmental uses. It is further desirable to design and isolate molecules having an activity which is regulatable by a desired substance. Assays can then be designed to detect the amount and presence of a desired substance, such as an analyte in a test sample, utilizing the ability of the analyte to directly or indirectly (e.g., by competition) regulate the molecule's activity. Assays can then be designed which utilize these regulatable activities.

DESCRIPTION OF THE INVENTION

The present invention relates to a chimeric target molecule having an activity which can be regulated or modulated by a binding molecule. The invention also relates to methods of using the chimeric target molecule to detect the presence and/or amount of a desired analyte in a sample. The analyte is a binding molecule, or a competitor of a binding molecule, which binding molecule, upon binding to the target molecule, alters the activity of the target molecule in a detectable way. In one aspect of the invention, a binding molecule binds to the chimeric molecule, inactivating it. An analyte in a test sample competes and/or displaces the binding molecule from the chimera, reactivating it. The reappearance of activity in the presence of the analyte indicates its existence and amount in the test sample. Another aspect of the invention relates to a binding molecule which regulates a chimeric target molecule and methods of producing it.

In accordance with the present invention, a desired target molecule (TM) can be modified to have at least one binding site moiety (BSM) to which a binding molecule (BM) can attach. Upon attachment of the BM to the BSM, an activity associated with the TM is altered in a detectable way, e.g., increasing or reducing the activity of the TM. Thus, the BSM can act as a regulatory switch, turning on or off (all or in part) an activity of a desired TM in response to the binding of a BM. The BSM can also be selected so that binding of the binding molecule regulates the activation of the target molecule. In accordance with the present invention, a mimetope is the preferred BSM. A BSM can be engineered into a target molecule by the insertion of sequences, by the replacement of sequences present in the molecule with new sequences, by mutagenesis of sequences already present in the molecule, etc. Engineering can be accomplished according to methods available to the skilled worker.

The target molecule can be selected for a desired detectable activity. For example, the TM can be: β-lactamase: P. Soumillion et al., J. Mol. Biol., 237:415:-422, 1994; Plasmin: L. Jespers et al., conference communication; Prostate specific antigen: R. Ecrola et al., Biochem. Biophys. Res. Comm., 200:1346-1352, 1994; Subtilisin: P. Soumillion et al., Appl. Biochem. Biotechnol., 47:175-190, 1994; Trypsin: D. R. Corey et al., Gene, 128:129-134, 1993; Alkaline phosphatase: J. McCafferty et al., Prot. Enging., 4:955-961; β-galactosidase: I. N. Maruyama et al., Proc. Natl. Acad. Sci. USA, 91:8273-8277, 1994; Staphylococcal nuclease: J. Ku & P. G. Schultz, Bioorg. Med. Chem., 2:1413-5, 1994; and J. Light & R. A. Lerner, Bioorg. Med. Chem., 3:955-67, 1995; Glutathione transferase: M. Widersten & B. Mannervick, J. Mol. Biol., 250:115-122, 1995; Lysozyme: K. Maenaka et al., Biochem. Biophys. Res. Comm., 218:682-687, 1996; and Catalytic antibodies: K. D. Janda et al., Proc. Natl. Acad. Sci USA, 91:2532-2536, 1994.

The above-mentioned target molecules have been displayed on phage. They are directly amenable to the method of selection of BSM. Other enzymes can also be displayed on phage and are useful for the present invention, e.g., esterases, pyruvate kinase, glucose oxidase, lactate dehydrogenase, glucose-6-phosphate dehydrogenase, luciferase. The TM can also be a protein possessing a fluorescent activity (e.g., green fluorescent protein, GFP: Chalfie et al., 1994, Science, 263:802; Cheng et al., 1996, Nature Biotechnology, 14:606; Levy et al., 1996, Nature Biotechnology, 14:610) which is modulated by binding of a BM to a BSM contained within the fluorescent protein. The TM can also be a regulatory molecule which activates/inactivates a second molecule having a detectable activity. For instance, a GTPase activating protein (GAP) stimulates a G-protein, such as ras. The ability of a GAP to activate a G-protein can be modulated by engineering a BSM into the GAP. Upon attachment of a BM to the BSM of a modified GAP, the stimulating activity of the GAP can be modulated. Its upstream effect on G-proteins can be monitored, e.g., by measuring a GTPase activity of the G-protein. See, e.g., Trahey and McCormick, Science, 238:542-545, 1987. The TM can also be a subunit of another protein which itself possesses enzymatic or another detectable activity. Additionally, the TM can be a nucleic acid enzyme, e.g., a ribozyme, a hammerhead enzyme, RNAse P, or a hairpin enzyme. If a nucleic acid is used as the target molecule, the engineered binding site moiety would usually comprise nucleotides, either modified or naturally-occurring. The TM can also be transcription activators and repressors regulated in in vitro transcription and translation systems; detection of activity can be accomplished at the level of the activity of the expressed enzyme or fluorescent molecule.

The activation of a chimeric molecule can also be regulated by a BM. The simplest example of activation is the proteolytic cleavage of a peptide bond in a zymogen to transform it into an enzyme. A classical example is the activation of a serine protease, or more specifically the activation of chymotrypsinogen into chymotrypsin by proteolytic cleavage of the peptide bond Arg15-Ile16 by trypsin. An antibody binding to an epitope or a mimotope engineered in the region of the cleaved peptide bond can inhibit the activation. Another example is the inhibition of the phosphorylation or dephosporylation of an enzyme whose activity is regulated by its state of phosphorylation. Glycogen phosphorylase is an example: when it is phosphorylated on Ser14, it is essentially in its active form, dephosphorylation deactivates the enzyme. Binding of an antibody to a engineered epitope or mimotope in the vicinity of the phosphorylation site would interfere with the activation/deactivation mechanism by phosphorylase kinase and phosphoprotein phosphatase respectively.

More generally any postraductional modification of an enzyme, that contributes to modulate its activity, can be interfered with by binding a foreign molecule to a BSM (e.g., an antibody).

The term “chimeric” target molecule, e.g., a “chimeric enzyme,” means the resultant product after the binding site moiety has been inserted into the target molecule or after a portion of the target molecule has been replaced by the binding site moiety. For clarity, before engineering of the BSM, the target molecule is referred to as the starting target molecule. Thus, if an enzyme is the starting material, it is referred to as the “starting enzyme.” After engineering of the BSM, the starting enzyme is identified as a “chimeric enzyme.” In the examples below, β-lactamase is used as a starting enzyme into which a binding site moiety comprising amino acids, is engineered to produce a chimeric enzyme. It is chimeric because it is comprised of amino acids of the starting enzyme and amino acids of a binding site moiety.

Target and chimeric molecules can be prepared by methods which are available in the art. For example, genetic engineering can be employed to prepare target and chimeric molecules which comprise amino acid or nucleotide residues. In one embodiment, a cloned gene is employed as the starting material for the starting target molecule and resultant chimeric target molecule. In the examples described below, the cloned gene for the starting enzyme β-lactamase serves as the beginning material to produce the chimeric enzyme. The BSM can be engineered into the starting TM using the various methods available to the skilled worker, e.g., Kunkel, Proc. Natl. Acad. Sci., 82:488-492, 1985; Brennan et al., Proc. Natl. Acad. Sci., 92:5783-5787, 1995. Engineering can also be accomplished using a replacement vector via homologous recombination. For the purposes of the present invention, when a sequence within a starting gene has been mutagenized to the extent that the amino acid sequence differs from the starting sequence, the polypeptide coded for the resultant gene is chimeric. It is chimeric since a different amino acid sequence, i.e., a binding site moiety, has been engineered into the starting target molecule. In the specific example where the starting material is an enzyme, and the enzyme is mutagenized by changing its nucleotide sequence, a resultant chimeric enzyme will comprise an amino acid binding site moiety which has replaced the naturally-occurring amino acid sequences. In one embodiment, the sequence of the gene encoding a wild type enzyme (or other polypeptide) is modified by the site directed mutagenesis according to the Kunkel or Eckstein protocols to introduce two restriction sites upstream and downstream from the region of the gene targeted for engineering; preferentially, a mutation is introduced in the coding sequence at the same time so that the encoded enzyme is inactive; the plasmid, phagemid or phage containing the modified gene will be called the “vector.” This vector is digested at the new restriction sites with the corresponding restriction enzymes and the small fragment encoding the sequence between the sites is discarded. In parallel, synthetic degenerate oligonucleotide libraries are prepared; they contain, in between the adequate restriction sites, degenerate nucleotide sequences encoding random replacements of the corresponding residues in the protein sequence. Alternatively, the wild type sequence is replaced by a longer nucleotide sequence that will encode the insertion of a random polypeptide in the corresponding position in the protein sequence. After restriction, the synthetic oligonucleotides are ligated with the purified large fragment of the digested vector and the ligation mixture is used to transform E. coli cells. Typically, libraries containing about 10⁶ and 10⁸ transformants are produced. Clones producing active enzymes are selected from these (see below). Recombination of clones producing active enzymes in two libraries where random mutations are introduced in different parts of the sequence is done to produce enzymes with discontinuous mimotopes.

The invention also relates to nucleic acids which code for a chimeric target molecule. Such a nucleic acid can further comprise various sequences, e.g., an expression control sequence(s) operably linked to a nucleotide sequence coding for the chimeric target molecule. The phrase “expression control sequence” means a nucleic acid sequence which regulates expression of a nucleic acid to which it is operably linked. Expression can be regulated at the level of the mRNA or polypeptide. Thus, the expression control sequence includes mRNA-related elements and protein-related elements. Such elements include promoters, enhancers (viral or cellular), ribosome binding sequences, transcriptional terminators, etc. An expression control sequence is operably linked to a nucleotide coding sequence when the expression control sequence is positioned in such a manner to effect or achieve expression of the coding sequence. For example, when a promoter is operably linked 5′ to a coding sequence, expression of the coding sequence is driven by the promoter. A nucleic acid coding for a chimeric also includes nucleic acids which hybridize to it, e.g., under stringent conditions, such as conditions that allow the selection of at least 95%, 99% nucleotide identity. For a chimeric TM which is a polypeptide, a nucleic acid coding for it includes, e.g., nucleotide degeneracy. Nucleic acids include DNA and RNA.

Chemical and/or synthetic methods can also be used to create the chimeric molecule, e.g., the methods of building compounds by combinatorial chemistry, as the skilled worker would know.

After modification of the starting target molecule to produce a resultant chimeric target molecule, it is desirable to select those chimeric molecules which have retained an activity of the starting target molecule. By the phrase, “the chimeric target molecule has an activity of the starting target molecule,” it is meant that the starting TM has an activity and the resultant chimeric TM has an activity, as well. The activity of the chimeric TM can be different quantitatively or qualitatively from the starting TM. By way of illustration, in the examples below, the starting enzyme is β-lactamase. β-lactamase is an enzyme which hydrolyzes a β-lactam bond. Various compounds can be used as substrates, including penicillins, cephalosporins, ampicillin, etc. The activity of the starting β-lactamase is hydrolysis of a β-lactam bond. A chimeric β-lactamase having a binding site moiety, either replacing or inserted in addition to naturally-occurring amino acids, will possess the ability to hydrolyse a β-lactam bind. This activity in the chimeric β-lactamase can be, e.g., greater or less than the starting enzyme (e.g., having a different Kcat), and/or have a different substrate specificity.

After modification by the engineering, e.g., insertion or replacement, of a BSM into the target molecule, the selection of the resultant molecule can be accomplished by various methods as the skilled worker would know. In one embodiment where genetic engineering is utilized, a gene coding for a target molecule, e.g., an enzyme, can be cloned into an expression vector suited for expression of a polypeptide in a desired host. Various hosts are contemplated, including, mammalian cells (e.g., human, monkey, or rodent, such as HeLa, COS, Ltk-, or CHO), insect cells (e.g., Sf9 or Drosophila), bacteria (e.g., E. coli, Streptococcus, or bacillus), yeast, fungi, or plants. See, also Methods in Enzymology, Volume 185, ed., D.V. Goeddel. Sf9 expression can be accomplished in analogy to Graziani et al., Oncogene, 7:229-235, 1992. Filamentous phage systems have been used to express and select peptides in bacteria that attach to binding molecules, including antibodies (Scott and Smith, 249:386-390, 1990; Grihalde et al., Gene, 166:185-195, 1995), streptavidin (Kay et al., 1993; Devlin et al., Science, 249:404-406, 1990), ribonuclease (Smith et al., Science, 228:1315-1317, 1985) and DNA (Rbar and Pabo, 1994). See, also, Jespers et al., Biotechnology, 13:378-382, 1995. See, also, Smith, Science, 228:1315-1317, 1985; Parmley and Smith, Gene, 76:305-318, 1985; de la Cruz et al., J. Biol. Chem., 263:4318-4322, 1988; Bass et al., Proteins, 8:309-314, 1990; Cwirla et al., Proc. Natl. Acad. Sci. USA, 87:6378-6382, 1990; Devlin et al., Science, 249:404-406, 1990; McCafferty et al., Nature, 348:552-554, 1990; Clackson et al., Nature, 352:624-628, 1991; Lowman et al., Biochemistry, 30:10823-10838, 1991; J. McCafferty et al., Port. Engng, pp. 955-961, 1991; Kang et al., Proc. Natl. Acad. Sci. USA, 88:4363-4366, 1991; Barbas et al., Proc. Natl. Acad. Sci. USA, 88:7978-7982, 1991; Roberts et al., Proc. Natl. Acad. Sci. USA, 89:2429-2433, 1992. Preferred polypeptides for filamentous phage expression systems are those which are properly folded on the phage, or at least, displayed on the phage in a fully active form. To identify whether a desired starting molecule is suitable, a nucleic acid coding for the molecule is cloned into the phage in a manner suitable for expression. The expressed molecule is then assayed for an activity in accordance with conventional methods. Engineering of a BSM into the starting molecule can then be accomplished in accordance with the above-mentioned procedures. See, e.g., Grihalde et al. Expression control sequences are selected for host compatibility and a desired purpose, e.g., high copy number, high amounts, induction, amplification, controlled expression, etc. Other sequences which can be employed, include enhancers such as from SV40, CMV, inducible promoters, or other elements which allow selective or specific cell expression.

A binding molecule can bind to a specific portion of a macromolecule called an epitope or a determinant. The epitope can be a linear determinant or a conformational determinant. See, e.g., Abbas et al., Cellular and Molecular Immunology, Second Edition, W.B. Saunders Co., 1991, especially, pages 47-49. A “mimetope” is a determinant which is recognized by the same binding molecule as a particular “epitope” but which has a different composition from the “epitope.” For example, a binding molecule can be an antibody which recognizes (i.e., binds to) an epitope comprising a linear sequence of amino acids. A “mimetope” of this epitope comprises a different linear sequence of amino acids but which is still recognized by the same antibody. The “mimetope” differs by at least one amino acid from the “epitope.” A mimetope can mime a hapten and other molecules, including nonproteinaceous molecules or moieties, e.g., carbohydrate, biotin, etc. As mentioned, the mimetope can also be a conformational determinant formed by amino acid residues or other constituents from separated portions of the chimeric molecule. Further, the mimetope can comprise constituents (e.g., amino acids) already present in the starting TM and which remained (i.e., were not replaced) in the chimeric TM. A mimetope can be selected as discussed above and below, e.g., in the examples, by engineering random amino acids into a target and screening for recognition by a desired binding molecule.

An advantage of employing a mimetope is that no knowledge of the structure of the epitope is required. This knowledge is in general difficult to acquire, particularly if the epitope is non-linear. In one aspect of the invention, a library of mimetopes is created and engineered, e.g., inserted, into a target molecule, preferably into a loop. The resultant chimeric molecule is then screened or selected for retention of activity. The mimetope can be a random sequence, e.g., containing five amino acids, preferably six amino acids (a random hexapeptide), or seven, eight, nine, ten, amino acids in length. In this aspect of the invention, upon identification of chimeric target molecules which have retained activity, they are then screened for recognition by the desired binding molecule. The binding molecule can be an antibody to a carbohydrate or other non-proteinaceous hapten or non-hapten, or an amino acid sequence. In especially the latter case, no sequence information is required to implement the invention.

The binding site moiety can be engineering into any desired position in the target molecule, including as a fusion with the N- and C-termini. One or more, e.g., 2, 3, 4, or 5, BSMs can be engineered into the target moiety at adjacent or different regions. Multiple engineering, e.g., insertions or replacements, to the target molecule can be made for a variety of reasons, e.g., to contribute to the mimetope (e.g., the mimetope can be comprised of amino acids contributed by engineering at two different sites in the target molecule), to provide more than one site to which a binding molecule can bind, to provide one site at which a BM activates the enzyme and another site at which a second BM inactivates an enzyme, etc. An advantage of inserting or replacing amino acid sequences with a mimetope at two sites (or more) is that a discontinuous mimetope can be constructed, providing for high affinity sites to which a binding molecule can attach. Preferably, as discussed above, the resultant chimeric TM retains at least some of its activity after engineering of the BSM. In addition, attachment of a BM to the BSM results in regulating the aforementioned activity of the chimeric target molecule. The latter two aspects, retention of an activity and regulation of the retained activity of the resultant chimeric molecule by a binding molecule, are preferred aspects of the invention. Thus, a preferred site of engineering, e.g., insertion, is a position where the activity of the TM is not eliminated but which, when replaced or modified by the addition of amino acid residues, can act as a regulatory switch for TM activity. By the phrase “whereby the activity of the chimeric target molecule is modulated upon binding of a binding molecule,” it meant that attachment of the binding molecule to the chimeric TM, preferably at the BSM, affects the activity of the chimeric TM in a detectable way. If the chimeric TM is an enzyme such as β-lactamase, the binding molecule will affect its activity in hydrolyzing the β-lactam bond. The affect of the binding molecule can be to reduce or even eliminate the activity, e.g., reduce or eliminate its ability to cleave the β-lactam bind. The binding molecule can also affect activity in other ways, e.g, activate it, increase it, change its specificity, activate it, etc.

Binding of the BM to the chimeric molecule, preferably at the BSM, can affect activity in various ways. For example, a chimeric TM can exist in at least two conformations, an active and inactive conformation. At equilibrium, a population of chimeric TMs will contain a mixture of molecules, some in the active and some in the inactive conformation. A BM can be selected that binds to an inactive conformation of a TM. When added to the chimeric TM population, attachment of the BM to the inactive TMs can shift the equilibrium of the mixture to the inactive conformation. As a consequence, the mixture will have less activity in the presence of the BM than in its absence. Thus, the binding molecule modulates the activity of the chimeric TM by shifting the population of chimeric TMs to an inactive conformation, thereby reducing the population's activity as a whole.

The binding molecule can inactivate the activity of the chimeric TM. By the term “inactivate,” it is meant that the activity of the chimeric TM is reduced or weakened. The binding molecule can inactivate the chimeric TM completely so that it possesses no, or only negligible, activity, or it can inactivate only part of its activity, e.g., where the Kcat is reduced. Attachment of the binding molecule to an inactive conformation of the chimeric TM is an example where the binding molecule inactivates the activity of the chimeric TM. A selected starting enzyme can be serine protease that can exist in two different conformations: an active and an inactive one. The inactive conformation is similar to that of the corresponding zymogen. The equilibrium can be shifted from the active into the inactive conformation by disrupting the salt bridge maintaining the enzyme in its active conformation; this can be done by a pH increase leading to deprotonation of the amino terminal of the peptide chain involved in the salt bridge or by chemical modification of this amino terminal. The energetics of the salt bridge are such that the active conformation is not strongly stabilized (2.9 Kcal/mol, see: A. R. Fersht, J. Mol. Biol., 64:497-509, 1972) so that the equilibrium can be relatively easily shifted to the inactive form. Binding of a monoclonal antibody to the amino acid terminal can shift the equilibrium by several orders of magnitude.

The site where a BSM is engineered, e.g., inserted into and/or replaced, in the TM can be selected by various ways as the skilled worker would know. For example, if the three-dimensional (3D) structure of the TM is known, a site can be selected by specifically identifying a desired location on the molecule to engineer. For some purposes, it may be desirable to select an exposed site on the surface of the target molecule, where the site is available for attachment by the binding molecule. 3D-structure can be determined according to empirical means, e.g., by crystallography, and/or, it can be deduced from known structures and amino acid sequence data. See, e.g., Holm and Sander, Science, 273:595-602, 1995. If the 3D-structure is not known, the site of engineering can be selected on the basis of other information, e.g., when the structure of the protein is not known, sites susceptible to limited proteolysis or sites strongly predicted to be loops by secondary structure prediction or by analysis of hydrophobic patterns are suitable for engineering, e.g., insertion or replacement. Alternatively, a BSM can be engineered at random positions within the TM.

The engineered site is preferably not at the active site, more preferably it is at a location remote from it, e.g., about 1, 5, 15, 20, or 25 Å from it. The activity must be regulatable by binding to the inserted or replaced sequence, irrespective of whether the modification is close or remote from the active site.

As mentioned above, an aspect of the present invention involves chimeric target molecules which have an activity that can be regulated or modulated by a binding molecule. In one preferred embodiment, random peptide sequences are engineered at a selected site on a target molecule, e.g., an enzyme. The first step is to select resultant chimeric molecules which retain the desired activity. If an enzyme activity is the desired activity, then a selection assay can be designed for it. Selection can be accomplished by color (e.g., where cleavage by the enzyme produces an end-product having a detectable color), by conferring resistance to clones expressing an active enzyme (e.g., drug resistance), etc. In one embodiment, screening is performed by plating a library on solid medium, adding a chromogenic or fluorogenic substrate, and observing product development in individual colonies. In vivo selection can be applied when the molecule is necessary for growth in the presence of antibiotic (antibiotic resistance; this technique is used with the beta-lactamase in the examples), or when the activity is used for complementation of an missing essential gene in auxotrophic bacteria (e.g., auxotrophy for an amino acid). In vitro selection can also be used when the enzyme is displayed on phage; e.g., WO 93/11242.

To measure the activity of the selected enzymes, any classical spectrophotometric, fluorimetric, potentiometric (pHstat) technique can be used. In the particular, the ORIGEN technology can be used for detection of product formation (JACS, 118, 9198-99). A next step of selection is to identify clones which bind to the binding molecule. Selection can be accomplished by antibody panning technique, column chromatography, etc. See, e.g., Grihalde et al., Gene, 166:187-195 (1995); McNally et al., J. Bio. Chem., 270:19744-19751, 1995; O'Neil and Hoess, Curr. Opin. Struct. Biol., 5:443-449, 1995. In one embodiment, the chimeric target molecule is expressed on the surface on the host cell (e.g., a bacteria, a insect cell, a mammalian cell) and selection can be accomplished without cell lysis. The chimeric target can also be expressed within the host cell and selection accomplished after, e.g., permeabilizing or lysing the cells, or otherwise making the expressed product accessible to the binding molecule.

A binding molecule means a molecule that specifically binds or attaches to a binding site moiety. By the term “specific,” it is meant that the binding molecule recognizes the defined sequence of amino acids within or including the amino acid sequence of the binding site moiety. Specificity can be a function of the linear amino acid sequence of the binding site moiety, alone, or in combination with amino acids originally present in the target molecule or at an insertion or replacement at another site. Various binding molecules can be employed, including antibodies, polypeptides, aptamers, nucleic acids, drugs, and chemical ligands. Antibodies can be monoclonal, polyclonal, single-chain, genetically-engineered antibodies, etc., as known in the art. See, e.g., Reiter et al., Nature Biotechnology, 14:1239-1245, 1996; Bird et al., Science, 242:423-426, 1988.

A chimeric target molecule can be used to detect the presence or amount of an analyte in test sample. In one embodiment, a chimeric TM is a chimeric enzyme. The chimeric enzyme is contacted with a (1) test sample containing an analyte, and (2) a substrate upon which the chimeric TM enzyme catalytically acts, to form a reaction mixture. The amount of analyte present in the reaction mixture is determined by monitoring or detecting the amount of catalysis of the substrate achieved by the chimeric enzyme, wherein the analyte modulates the catalysis by the chimeric enzyme. A test sample can be any sample containing an analyte whose presence or amount it is desired to be known, e.g., body fluids such as blood, serum, urine, feces, or lymph, tissue homogenates, biopsies, organ fluids, tissue culture medium, etc. By “analyte,” it is meant a molecule whose presence in a test sample is being detected. In one embodiment, the analyte is an antibody, such as an antibody specific for prostate specific antigen (PSA), carcinoma embryonic antigen (CEA), c-erbB2, products of oncogenes, viral (HIV or hepatitis), bacterial (staphylcoccal), and the chimeric TM is a chimeric enzyme. Alternatively, the analyte can be a polypeptide such as any of the aforementioned proteins or fragments thereof. Binding or attachment of the antibody to the chimeric enzyme can modulate catalysis of the substrate by the chimeric enzyme. Modulation of activity is discussed above. In a preferred example, the enzyme activity of the chimeric enzyme is reduced (inactivated) by the antibody. Thus, the presence of the analyte antibody in the test sample can be determined by monitoring or detecting the reduction of activity manifested by the chimeric enzyme, either as individual molecules or as a population. Alternatively, the analyte is a polypeptide. When the chimeric molecule is combined with an appropriate binding molecule, its activity is modulated. Addition of the analyte, competes and/or displaces the binding molecule, reversing its modulatory effect on the detectable activity. The enzyme assay can be performed in accordance with known procedures. For example, the activity can be monitored temporally, kinetically, or by end-point. The chimeric enzyme can be in solution or on a solid support, e.g., directly coupled or via biotin-strepavidin coupling, to materials such cellulose, Sephadex, plastics, polypropylene, polystyrene, polyvinyl, cellulose nitrate, polythylene, nylon, polymethylmetaacrylic, etc. The coupling can be accomplished as one having skill in the art would know. See, e.g., Methods in Enzymology, Volume 73, for various techniques on substrates, coupling, and assays in general. By the term “contacting” the chimeric molecule with a test sample containing analyte or binding molecule, it is meant that the analyte or binding molecule is brought into contact with the chimeric molecule by a desired means. The contact can be accomplished by: adding a test sample to a solution containing the chimeric TM, dipping a solid support containing the chimeric enzyme into a solution containing the analyte or BM, dropping a solution containing an analyte on to a solid support containing the chimeric TM, etc. If a substrate is used, e.g., where a chimeric TM is an enzyme, the substrate can be contacted with the chimeric enzyme at the same time as the analyte, or before or after, i.e., simultaneously or sequentially.

As mentioned, the chimeric TM can be any molecule having a desired activity, e.g., enzymatic, fluorescent, activating, complementary, etc. Assays for detecting an analyte can be tailored as one of ordinary skill in the art would know for monitoring or detecting the change in activity of the selected chimeric TM.

In another aspect of the present invention, the activity of a reaction mixture, comprising a chimeric enzyme and an analyte (a first binding molecule) which modulates the activity of the chimeric enzyme, can be further affected by a second binding molecule. The second binding molecule can act as a direct competitor of the analyte, competing for the same site as the analyte. In one embodiment, the analyte inactivates the activity of the chimeric TM. The second binding molecule acts as antagonist of the analyte, competing for the same site of the chimeric TM but ineffective in inactivating it. Consequently, addition of the second binding molecule will result in the restoration of activity in the reaction mixture. The second binding molecule can also antagonize the action of the analyte by inactivating the analyte, itself, without site-specific competition. In this embodiment, the second binding molecule can, e.g., be an antibody which prevents the analyte from attaching to the chimeric TM and thus reduces the analytes ability to inactivate the chimeric TM. The second binding molecule can be prepared in the same way as described above for the binding molecule.

The assays of the present invention are useful for medical, veterinary, environmental, and various diagnostic uses, e.g., for detecting diseases, pathogenic disorders, environmental contamination, tissue culture contamination, etc. For example: the presence of cancer in a patient can be determined by detecting the presence of a characteristic antigen or antibody. It is known that individuals with cancer can have elevated levels of various antigens, such as prostate-specific antigen (PSA) or carcinoma embryonic antigen (CEA).

In another aspect of the present invention, an analyte is a competitor of a binding molecule. The presence or amount of competition with the binding molecule is used to ascertain its presence. An example of such a process is described in mimetope recognized by a antibody specific for a desired molecule is prepared (in the example, it is prostate-specific antigen or “PSA”). Binding of the antibody to the mimetope reduces the activity of the chimeric molecule. The analyte (in the example, it is PSA) competes with the antibody for binding to the mimetope. Thus, if analyte is present, less of the antibody binds to the chimeric molecule. With less antibody bound to the chimeric molecule, the chimeric molecule is more active than in the absence of the analyte. This is illustrated in Example 3.

DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the insertion sites used to generate lib1 and lib3 libraries. lib1: 1. V103; 2. E104; 3. Y105. lib3: 4. T271; 5. M272. Catalytic site: 6. 570.

FIGS. 2A and 2B are schematics of the construction of a library lib1.

FIG. 3 is a schematic of the construction of a library lib3.

FIG. 4 and FIG. 5 show the inhibitory effect of antibody PSA19 on a mutant β-lactamase psa19A;302.

FIG. 5 is an expansion area of FIG. 4, representing the enzyme activity as a function of PSA19, between 0 and 37 nM.

For other aspects of the nucleic acids, polypeptides, antibodies, etc., reference is made to standard textbooks of molecular biology, protein science, and immunology. See, e.g., Davis et al. (1986), Basic Methods in Molecular Biology, Elsevier Sciences Publishing, Inc., New York; Hames et al. (1985), Nucleic Acid Hybridization, IL Press, Molecular Cloning, Sambrook et al.; Current Protocols in Molecular Biology, Edited by F. M. Ausubel et al., John Wiley & Sons, Inc; Current Protocols in Human Genetics, Edited by Nicholas C. Dracopoli et al., John Wiley & Sons, Inc.; Current Protocols in Protein Science; Edited by John E. Coligan et al., John Wiley & Sons, Inc.; Current Protocols in Immunology; Edited by John E. Coligan et al., John Wiley & Sons, Inc.

EXAMPLES Example 1

1. Construction of a Library in a Loop on the Rim of the Active Site of the β-lactamase Protein (lib1).

The loop on the rim of the active site, in the region encompassing V103-V105, was chosen as an insertion-replacement site because its position is close to the catalytic pocket and the sequence is poorly conserved in this region among class A β-lactamases. FIG. 1.

Two different lib1 libraries, lib1A-B and lib1D have been constructed on the basis of an inactivated vector. They both contain a six amino acid insert in replacement of residues E104--Y105 and V103--Y105, respectively. The activities of the lib1A-B and lib1D libraries were evaluated by plating samples of bacteria on plates with different ampicillin concentrations and counting the clones obtained after incubation at 37° C. or 23° C. These titrations allowed us to determine the conditions to unambiguously select clones with activities higher than 30-40 s⁻¹ (i.e., incubation at 37° C. for 17 hours on LB plates containing 10 μg/ml of freshly dissolved ampicillin). The activities of the libraries are low since only 0.05% and 0.08% of their clones are able to grow on 10 μg ampicillin/ml at 37° C. Activity measurements carried out on several individual clones selected in those conditions confirmed this activity. See, Tables 1-3. The sequence variability is moderate and clones with shortened sequences are present; this was observed despite the fact that the degenerated oligonucleotides used to construct the inserts were purified on acrylamide (after the single strand to double strand DNA conversion step and before ligation into the vector); the purification step is efficient but insertions are probably not well tolerated in this region, consequently, the rare active clones corresponding largely with shortened sequences are selected.

The active fractions of the lib1A-B and lib1D libraries have been produced on a large scale (=lib1C₂₋₄ and lib1D₂). See, e.g., FIGS. 2A and 2B.

2. Construction of a library in the loop preceding the α11 Helix of β-lactamase (lib3).

The loop preceding the α11 helix (residues 271-272) of β-lactamase was chosen as an insertion site because of its position relatively close to the catalytic pocket and its poor sequence conservation among the known β-lactamases. This region is also well located with regard to the insertion site of the lib1 library (residues 103-106) for the construction of a non linear epitope. Indeed, these two regions lie on opposite edges of the active site. See, FIG. 1.

In one experiment, we have exchanged the amino acids T₂₇₁ and M₂₇₂ of the β-lactamase for a degenerated sequence of 5 residues to give the lib3d library. The activity of the library was interesting since 2 to 3 percent of the clones proved to be active (this represents about 8×10⁴ different clones). The methionine at position 272 is strongly conserved in active clones. See, Table 4. Moreover, about one third of the clones selected on 10 μg ampicillin contained sequences shorter than 5 residues. This results from the presence during the cloning of the degenerated insert into the β-lactamase vector of a small percentage of shortened double strand oligonucleotide (shorter insert clones are afterward strongly selected since they are more active).

Although the lib3 d library was sufficiently large and active to be recombined with lib1, its variability prompted us to construct a second library in the same region but replacing only residue T₂₇₁. The size of the insert was increased to 6 amino acids (instead of 5) in order to take into account the more remote position of the new insertion site. The library produced, lib3f, proved to be very active since about 7% of the clones were able to grow on 10 μg ampicillin/ml at 37° C. Sequencing of several clones selected in those conditions indicated that active clones have a wide sequence variability and do not contain shortened insertion sequences. See, Table 5. This last point results from an improvement in the cloning procedure in which the degenerated oligonucleotides were this time purified on acrylamide gel (after the single strand to double strand DNA conversion step).

The active fractions of the lib3d and lib3f libraries have been purified (=lib3E and lib3G, respectively) and stored as phage and DNA libraries (large DNA stocks were produced on CsC1 gradients). See, FIG. 3. The size (about 4×10⁶ different active clones) and activity of the lib3G library should allow direct affinity selections with psa antibodies.

3. Recombination of the lib1 and lib3 Libraries.

Several libraries have been constructed. In these, random peptide sequences have been inserted in the region 103-105 and 271-272 of the sequence of the R-Tem β-lactamase (J. G. Sutcliffe, Proc. Natl. Acad. Sci., 75:3737-3741, 1995). These libraries (lib1C2, 1C4 and 1D2 in the 103-105 region and lib3E and 3G in the 272-272 region) were selected on ampicillin and contain essentially clones whose kcats are higher than 40 s⁻¹ (i.e., ≧4% of wild type activity). The size of the lib1 and lib3 libraries are about 1×10⁴ and 4×10⁶ clones, respectively.

A further selection of the lib3G library on ampicillin was carried out before recombining it with the lib1 library. The lib3G is indeed very large and has a wide diversity of sequences so that we could afford to select only the most active clones in it. This should increase the chances of obtaining an active recombinant library. The lib3G library was selected on 30 μg ampicillin/ml at 37° C., which allowed us to select 10% of its clones. In this way, the activity of the library was increased by a factor 1.5.

To construct the recombinant library, the lib1C2, 1C4 and 1D2 libraries were pooled and were recombined with the 30 μg ampicillin/ml-selected lib3G library (=lib3H). The library obtained proved to be very active as about 20% of its clones were able to grow on 10 μg ampicillin/ml at 37° C. This means that 20% of its clones have activities higher than 40 s⁻¹. The sequencing of these clones showed that only 2 clones/13 contained simultaneously a full insert in both locations (table 6). This frequency results from the presence in the lib1 library of about 50% of shortened inserts. To determine the activities of the correctly-constructed clones we measured the kcats of several clones not selected on ampicillin. Interestingly, among 12 clones analysed only 2 had activities lower than 10 s⁻¹ (table 7). It seems therefore that the well-constructed clones possess relevant activities even though the majority of them are probably unable to grow on 10 μg ampicillin/ml.

Several different cloning approaches were needed to finally obtain a recombinant library of great size. The best library has been produced on a large scale (=lib rec4b) and contains about 5 10⁷ different clones. This library was not submitted to any further treatment before selecting on psa antibodies (selection on ampicillin can be used to amplify the proportion of constructed clones).

Example 2

1. Selection for Binding by Monoclonal Antibodies Psa10 and Psa66.

Three rounds of selection were carried out on the lib3j and rec4B libraries by panning on streptavidin-coated magnetic beads (Dynabeads M280 from Dynal AS, Oslo, Norway) saturated with biotinylated psa10 and psa66 antibodies as selecting agents (from CanAg Diagnostics AB, Gothenburg, Sweden). The goal was to extract from these libraries the phages displaying mutant β-lactamases with high affinity for the antibodies. In each case an amplification factor higher than 1000-fold was obtained between the first round of selection and the third one (ratio of the number of phages eluted between the 3rd and 1st round of selection-elution at low pH). This indicates that an efficient selection was achieved. After the third round of selection, the effect of psa antibody binding on activity on PenG as substrate was determined on the libraries selected; a slight inhibition was observed in the case of the psa66-selected rec4b library (˜20% at 3.3 10⁷M of psa66). This inhibitory effect reached 40-45% when larger substrates (PADAC or Centa) are used.

The characterization of the phages eluted from the third round of selection indicated that a strong selection was exerted on the lib3 region of the libraries. Only a low sequence variability is indeed observed at this location (tables 8 and 9). On the other hand, no sequence conservation could be found in the lib1 region; this region might nevertheless contribute to the binding of the antibody as the wild type residues are replaced in these clones. It is believed, however, that the psa10 and psa66 epitopes are probably linear (communication from CanAg). In the case of the phages selected on psa66, a SX₍₁₋₀₎L/IQ consensus motif could be derived. This motif was also present in clones isolated previously from the library created in the ω-loop (lib2) after selection on the same antibody (this motif is not found in the psa sequence). With psa66, we have thus selected a mimotope. Unexpectedly, a HPQ sequence was found in several clones selected on psa10. This suggests that in this case the selection was carried out, at least partially, on streptavidin instead of on the antibody. As a slight precipitate was visible in the biotinylated preparation of psa10, it is possible that the antibody was denaturated and did not coat the streptavidin beads. We tested therefore whether the activity of the lib3j and rec4b libraries, selected on psa10, could be regulated by streptavidin binding but no positive results were obtained. We just noticed a faint stimulation in the case of the rec4b library. At present, the characterization of the libraries selected on psa10 has not been pursued.

Several individual clones selected on psa66 from the lib3j and rec4b libraries have been analysed. They all possess high activities (table 9). Whereas no regulation was found in the case of the clones isolated from the lib3j library, most of the clones selected from the rec4b library showed a substantial psa66-dependent modulation of their activity. The level of modulation depends on the clones (there is a large diversity of clones as the sequence in the lib1 region of the library is variable) but ranges mainly between 30 and 60% of inhibition on PADAC (R. N. Jones et al., Clin. Microbiol., 15:677-683, 1982) or Centa (R. N. Jones et al., Clin. Microbiol., 15:954-958, 1982) (at 3.3×10⁻⁷ M of psa66). This percentage can reach more than 70% when the concentration of psa66 is increased to 1.7×10⁻⁶ M. The inhibition is less important when PenG is used as a substrate. This difference of behavior results probably mainly from the difference in size of the substrates, the larger substrates being less rapidly hydrolysed in the presence of the bound antibody. The maximum inhibition (at [psa66]=∞) has been calculated for one of the best regulated clone (p66Rb316) and reaches 68% on PADAC and 75% on Centa (kd=1.2 10⁻⁷ M). As the psa66-selected rec4b library seems to contain many different individuals we can not exclude that better regulated clones are present in it.

2. Selection for Binding on Monoclonal Antibody Psa19.

Three rounds of selection were carried out on the lib3j library by panning using the psa19 antibody (CanAg diagnostics AB, Gothenburg, Sweden). Several clones were analysed for regulation of activity by psa19 binding. To perform such activity assays, the phage enzyme is diluted in 50 mM phosphate buffer at pH 7, at a concentration of 2.4×10⁻⁹ M. The PSA19 monoclonal antibody is added at a final concentration which varies between zero and 1.3 μM. After 10 minutes, the substrate (benzyl-penicillin) is added at a final concentration of 5×10⁻⁴ M. The activity is measured by determination of the rate of decrease of the absorbance at 232 nm. A plot of the inhibitory effect of the monoclonal antibody PSA19 on the catalytic activity of the mutant β-lactamase on phage identified as psa19Aj302 and extracted from the lib3j library is shown in FIGS. 4 and 5. FIG. 5 is a blow-up of FIG. 4, it represents the activities as a function of [PSA19] between 0 and 37 nM. The activity is reduced to 60% at a PSA 19 antibody concentration of 4×10⁻⁹ M and to 17% at saturation. This allows detection of the analyte PSA itself at a nM concentration by observation of an increase in activity. See FIGS. 4 and 5.

Three rounds of selection were also applied to the rec4B library using the psa19 antibody. A clone was found whose activity was regulated by psa binding. The phage enzyme was diluted in 50 mM phosphate buffer at pH 7, at a concentration of 2.4×10⁻⁹ M. The PSA antibody is added at a final concentration which varies between zero and 1.3 μM. After 10 minutes, the substrate (benzyl-penicillin) is added at a final concentration of 5×10⁻⁴ M. The activity is measured by determination of the rate of decrease of the decrease of the absorbance at 232 nm. A kcat of 134 s^(″1) was found in absence of psa19. Psa19 binding inhibits the activity to 8% of that found in absence of antibody; half of the effect is observed at a concentration of psa19 of 50 nM (Kd 5×10⁻⁸ M for the complex between psa19 and the β-lactamase mutant).

3. Summary.

Two large libraries have been constructed, lib3j and rec4b. These libraries are very active and permitted the selection on antibodies of clones whose kcat values range between 3 and 13% that of the wild-type Fdbla clone. The construction of an active library was assumed to be a prerequisite in the finding of regulable β-lactamase mutants.

A single successful affinity selection of the rec4b library has allowed to identify clones that are strongly regulated by their binder, i.e., in this case by the psa66 antibody.

EXAMPLE 3

The lib1 library was analysed by panning directly on the Dynabeads M280 to extract phage enzymes regulated by binding to streptavidin. A clone was found with a kcat of 20 s⁻¹, a binding constant of streptavidin Kd=1.2×10⁻⁷ and an inhibition factor of 1.3. Addition of biotin at a concentration of 5×10⁻⁷ restored the activity to that observed in absence of streptavidin. The sequence of the peptide inserted between L₁₀₂ and S₁₀₆ in replacement of V₁₀₃-Y₁₀₅ was YHPQNS.

Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The preceding preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever.

The entire disclosure of all applications, patents and publications, cited above and in the figures are hereby incorporated by reference.

From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention, and without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.

TABLE 1 Sequences and activities of lib1 A clones selected on 10 μg ampicillin/ml at 37° C. Clones Inserted sequence Kcat (s⁻¹)^(a) FdBla Val₁₀₃ - - - - Glu₁₀₄ Tyr₁₀₅ Ser₁₀₆ ND Lib1A-01 - - - - Val Ser 29 Lib1A-02 - - - Leu His Ser 16 Lib1A-03 Lys Ala Gly Ser 70 Asp Gly (SEQ ID NO: 1) Lib1A-04 Gly Gly Pro Arg 15 Ser Trp (SEQ ID NO: 2) Lib1A-05 Lys Asn Cys Gly 12 Lys Cys (SEQ ID NO: 3) Lib1A-06 Asp Val Pro Gly 47 Ala Gly (SEQ ID NO: 4) Lib1A-07 Lys Ser Gly Glu His 145  Ser (SEQ ID NO: 5) Lib1A-08 - - - Pro Gly Gly 74 Lib1A-09 Arg Ala Gly Asn 265  His Ser (SEQ ID NO: 6) Lib1A-10 Asp Pro Pro Gly 9 Tyr Gly (SEQ ID NO: 7) ^(a)kcats from phages produced at 23° C. (PenG) ND: not done

TABLE 2 Sequences and activities of lib1C₄ clones Clones Inserted sequence Kcat (s⁻¹)^(a) FdBla Val₁₀₃ - - - - Glu₁₀₄ Tyr₁₀₅ Ser₁₀₆ ND LibC4-11 Arg Phe Gly Asn 159 Asp Trp (SEQ ID NO: 8) LibC4-12 - - - - Trp Trp ND LibC4-13 - - Arg Ser His Trp ND (SEQ ID NO: 9) LibC4-14 - - - - Gln Trp ND LibC4-15 Asp Gln Met Gly ND Gly Gly (SEQ ID NO: 10) LibC4-16 Arg Ala Gly Ser  64 Thr Trp (SEQ ID NO: 11) LibC4-17 Lys Gly Gly Leu 721 Glu Ser (SEQ ID NO: 12) LibC4-18 - - - - Ser Asn ND LibC4-19 - - - - Glu Gly ND ^(a)kcats from phages produced at 23° C. (PenG); ND: not done

TABLE 3 Sequences and activities of lib1D₂ clones Clones Inserted sequence Kcat (s⁻¹)^(a) FdBla Leu₁₀₂ - - - Val₁₀₃ Glu₁₀₄ Tyr₁₀₅ Ser₁₀₆ ND Lib1D2-02 - - - Val Gly Gly ND Lib1D2-03 - - - Val Thr Tyr ND Lib1D2-04 Phe - - - Gly Thr Trp ND Lib1D2-05 Leu Pro Asn Leu Asp 224 Thr (SEQ ID NO: 13) Lib1D2-06 - - - Ile Ser Trp ND Lib1D2-07 Asn Arg Ser Gly Ser 2506  Trp (SEQ ID NO: 14) Lib1D2-08 Asp Val Ser Gly Gly 337 His (SEQ ID NO: 15) Lib1D2-09 Leu His Ser Gly Gly Trp ND (SEQ ID NO: 16) Lib1D2-10 Ser Arg Ala Gly Gly ND Tyr (SEQ ID NO: 17) ^(a)kcats from phages produced at 23° (PenG) ND: not done

TABLE 4 Sequences and activities of several clones from the lib3d library picked from among the 3% most active ones Clones Inserted sequence Kcat (s⁻¹)^(a) FdBla Ala₂₇₀ - - - Thr₂₇₁ Met₂₇₂ Asp₂₇₃ Glu₂₇₄ ND Arg₂₇₅ Lib3-01 - - - Ser Met 1133 Lib3-02 - - Ala Thr Thr 203 Lib3-03 Thr Ala Lys Met Asp 127 (SEQ ID NO: 18) Lib3-04 Pro Pro Thr Val Ser Met 92 (SEQ ID NO: 19) Lib3-05 Arg Gln Ser Thr Met 48 (SEQ ID NO: 20) Lib3-06 Asp - - Asp Arg Ala 1.1 Lib3-07 Gly Arg Thr Thr Met 44 (SEQ ID NO: 21) Lib3-08 Ser Asp Gln Pro Leu Leu 140 (SEQ ID NO: 22) Lib3-09 His Thr Ala Ser Met 137 (SEQ ID NO: 23) Lib3-10 - - - Asn Gly 278 Lib3-11 Lys Ser Val Gly Leu ND (SEQ ID NO: 24) Lib3-12 Ala Asn Ile Ser Leu ND (SEQ ID NO: 25) Lib3-13 - - - Asn Ile ND Lib3-14 Pro Val Ala Pro Ile ND (SEQ ID NO: 26) Lib3-15 Arg Pro Thr Thr Leu ND (SEQ ID NO: 27) Lib3-16 Pro Asn Ala Asn Met ND (SEQ ID NO: 28) Lib3-17 - - Ala Thr Thr ND ^(a)kcats from phages produced at 23° C. (PenG) ND: not done

TABLE 5 Sequences and activities of lib3f clones selected on 10 μg ampicillin/ml at 37° C. Clones Inserted sequence Kcat (s⁻¹)^(a) FdBla Ala₂₇₀ - - - - - Thr₂₇₁ Met₂₇₂ Asp₂₇₃ ND Glu_(274 Arg) ₂₇₅ (SEQ ID NO: 40) Lib3-18 Ala Thr Ser Phe Ala 208 Phe (SEQ ID NO: 29) Lib3-19 Arg Arg Lys Gln  32 Pro Thr (SEQ ID NO: 30) Lib3-20 Thr Ala His Val Ala  99 Ser (SEQ ID NO: 31) Lib3-21 Thr Asn Lys Gln  73 Pro Ser (SEQ ID NO: 32) Lib3-22 Lys Ser Tyr Thr Pro Gln  85 Glu (SEQ ID NO: 33) Lib3-23 Lys Trp Asn Tyr ND Thr Thr (SEQ ID NO: 34) Lib3-24 Gly Glu His Glu 114 Ala Gly (SEQ ID NO: 35) Lib3-25 Glu Glu Asn Gly Gln 100 Arg Pro (SEQ ID NO: 36) Lib3-26 Gln Leu Gln Val 186 Pro Pro (SEQ ID NO: 37) Lib3-28 Ala Pro Gly Asn  64 Asp Gly (SEQ ID NO: 38) Lib3-29 Ala Gly Ala Thr 111 Tyr Glu (SEQ ID NO: 39) ^(a)kcats from phages produced at 23° C. (PenG) ND: not done

TABLE 6 Sequences and activities of rec1 clones selected on 10 μg ampicillin/ml at 37° C. Clones Inserted Sequence Kcat (s⁻¹)^(a) FdBla Leu₁₀₂ - - - Val₁₀₃ Glu₁₀₄ Tyr₁₀₅ Ser₁₀₆ - - - Ala₂₇₀ - - - Thr₂₇₁ Met₂₇₂ ND Rec1-01 Glu Arg Ser Gly His Trp - - - - - Thr 145 (SEQ ID NO: 41) Rec1-03 - - - Val Glu Tyr Arg Thr Ala Lys Val Ser  57 (SEQ ID NO. 44) Rec1-04 - - - Val Thr Trp Gln Lys Val Glu Pro Ser  61 (SEQ ID NO. 45) Rec1-05 - - - Val Leu Gly - - - - - His 145 Rec1-06 - - - Val Gln Gly Thr Gly Val Tyr Pro Ser 170 (SEQ ID NO. 46) Rec1-07 - - - Cys Met Gly Gln Gly Pro Trp Ala Ser 380 (SEQ ID NO. 47) Rec1-09* - - - Ile Glu Gly Ile Gly Asp Tyr Ser Lys 251 (SEQ ID NO. 48) Rec1-10 - - - Val Asp Trp Thr Gly Asn Gln Ala Thr  93 (SEQ ID NO. 49) Rec1-11* - - - Val Ser Gly Ser Asn Gly Glu His Ser  54 (SEQ ID NO. 50) Rec1-12 - Leu Ala Ser Gly Tyr Ser Gly His Glu Pro Thr 139 (SEQ ID NO: 42) (SEQ ID NO. 51) Rec1-14 - - - Val Pro Tyr Asp Ser Lys Glu Thr Ser 304 (SEQ ID NO. 52) Rec1-15* - - Val Arg Ser Gly Pro Trp Thr Ala Arg Trp Ala Asn  72 (SEQ ID NO: 43) (SEQ ID NO. 53) Rec1-16 - - - Val Met Gly Thr Ala Asn Glu His Thr 155 (SEQ ID NO. 54) ^(a)kcats from phages produced at 23° C. (PenG) ND: not done; *clones containing an additional mutation (Arg₂₇₅ ^(L)).

TABLE 7 Activities of rec1 clones not selected on ampicillin. clones Kcat (s⁻¹)^(a) rec1-17 57 rec1-18 12 rec1-19 187 rec1-20 32 rec1-21 32 rec1-22 1.8 rec1-23 15 rec1-24 224 rec1-25 67 rec1-26 155 rec1-27 4.6 rec1-28 20 ^(a)kcats from phages produced at 23° C. (PenG)

TABLE 8 Clones selected on psa 10. Clones Inserted Sequences Kcat −psa66/+psa66 (s⁻¹)* FdBla Val₁₀₃ Glu Tyr Thr₂₇₁ Met S = PenG [psa 10] = 3.3 10⁻⁷M P10Aj3 Library^(a) 187/179 P10Aj301 Val Glu Tyr His Pro Gln Asn Asp Asp Met ND (SEQ ID NO: 59) P10Aj302 Val Glu Tyr His Pro Gln Asn Asp Asp Met ND (SEQ ID NO: 60) P10Aj303 Val Glu Tyr His Pro Gln Asn Asp Asp Met ND (SEQ ID NO: 61) P10Aj304 Val Glu Tyr His Pro Gln Gly Asp Asn Met ND (SEQ ID NO: 62) His Pro Gln Gly Asp Ser Met (SEQ ID NO: 63) P10Aj305 Val Glu Tyr His Pro Gln Asn Asp Asp Met ND (SEQ ID NO: 64) [psa 10] = 3.3 10⁻⁷M P10RB3 Library^(b) 52/52 P10RB311 Val Arg Tyr Ser Asp Gly His Arg Leu Met (Arg₂₇₅→Leu) ND (SEQ ID NO: 65) P10RB312 VaI Lys Ser Gly Val Ala Ser Asp Gly His Arg Leu Met (Arg₂₇₅→Leu) ND (SEQ ID NO: 55) (SEQ ID NO: 66) P10RB313 Val Lys Ser Gly Asn Thr Trp Ser Asp Gly His Arg Leu Met (Arg₂₇₅→Leu) ND (SEQ ID NO: 56) (SEQ ID NO: 67) P10RB314 Val Asp Arg Thr Lys Gly Ser Asp Gly His Arg Leu Met (Arg₂₇₅→Leu) ND Trp (SEQ ID NO: 57) (SEQ ID NO: 68) P10RB315 Val Asp Gly Pro Asn Gly Ser Asp Gly His Arg Leu Met (Arg₂₇₅→Leu) ND His (SEQ ID NO: 58) (SEQ ID NO: 69) ^(a)lib3j and ^(b)rec⁴⁶ phages from the third round of selection *kcats from phages produced at 23° C.

TABLE 9 Clones selected on psa66. Clones Inserted Sequence Kcat −psa66/+psa66 (s⁻¹)*; % age inhibition FdBla Val₁₀₃ Glu Tyr Thr₂₇₁ Met S = PenG S = PADAC S = Centa [psa66] = 3.3 10⁻⁷M [psa66] = 3.3 10⁻⁷M P66Aj3 Library^(a) 444/425; 04% ND P66Aj306 Val Glu Tyr Thr Pro Gly Ser Leu Gln Met ND 67.9/65.8; 03% (Arg₂₇₅→Leu) (SEQ ID NO: 71) P66Aj307 Val Glu Tyr Ser Ala His Gln Asp Tyr Ile ND 42.4/42.4; 00% (Arg₂₇₅→Leu) (SEQ ID NO: 72) P66Aj308 Val Glu Tyr Thr Pro Gly Ser Leu Gln Met ND ND (Arg₂₇₅→Leu) (SEQ ID NO: 73) P66Aj309 Val Glu Tyr Thr Pro Gly Ser Leu Gln Met ND ND (Arg₂₇₅→Leu) (SEQ ID NO: 74) P66Aj310 Val Glu Tyr Thr Pro Gly Ser Leu Gln Met ND ND (Arg₂₇₅→Leu) (SEQ ID NO: 75) [psa66] = 3.3 10⁻⁷M [psa66] = 3.3 10⁻⁷M [psa66] = 1.7 10⁻⁶M [psa66] = 3.3 10⁻⁷M [psa66] = 1.7 10⁻⁶M P66RB3 Library^(b) 405/326; 20% 23.8/14.2; 41% ND 12.2/6.7; 45% ND P66RB316 Val Lys Gly Asp Gly Ser Arg Ile Gln Met 182/134; 26% 25.1/13.6; 46% 20.5/7.8; 62% 14.7/7.2; 51% 15.4/4.1; 73% (Arg₂₇₅→Leu) (SEQ ID NO: 76) P66RB317 Val Lys Gly Gly His Gly Ala Thr Leu ND 28.2/26.5; 06% ND ND ND (SEQ ID NO: 70) P66RB318 Val Val Gly Asp Gly Ser Arg Ile Gln Met ND 28.6/11.9; 58% ND 13.8/5.8; 58% 13.3/3.5; 74% (Arg₂₇₅→Leu) (SEQ ID NO: 77) P66RB319 Val Gln Gly Asp Gly Ser Arg Ile Gln Met ND 47.4/32.6; 31% ND ND ND (Arg₂₇₅→Leu) (SEQ ID NO: 78) P66RB321 ND ND ND 17.2/09.3; 46% ND ND ND P66RB322 ND ND ND 27.2/23.8; 13% ND ND ND P66RB323 ND ND ND 19.0/13.2; 31% ND ND ND P66RB324 ND ND ND 22.4/15.2; 32% ND ND ND P66RB325 ND ND ND 21.6/14.9; 31% ND ND ND P66RB326 ND ND ND 19.6/19.2; 02% ND ND ND P66RB327 ND ND ND 20.5/19.6; 04% ND ND ND P66RB328 ND ND ND 29.2/15.8; 46% ND ND ND P66RB329 ND ND ND 26.3/14.3; 46% ND ND ND P66RB330 ND ND 6015/4273; 29% 647/444; 31% ND 33.5/46.2; −32% 33.2/53.7; −62% P66RB331 ND ND ND 25.7/14.1; 45% ND ND ND P66RB332 ND ND ND 25.2/23.5; 09% ND ND ND ^(a)lib3j and ^(b)rec4b phages from third round of selection *kcats from phages produced at 23° C.

78 1 6 PRT Artificial Sequence Mimetope 1 Lys Ala Gly Ser Asp Gly 1 5 2 6 PRT Artificial Sequence Mimetope 2 Gly Gly Pro Arg Ser Trp 1 5 3 6 PRT Artificial Sequence Mimetope 3 Lys Asn Cys Gly Lys Cys 1 5 4 6 PRT Artificial Sequence Mimetope 4 Asp Val Pro Gly Ala Gly 1 5 5 6 PRT Artificial Sequence Mimetope 5 Lys Ser Gly Glu His Ser 1 5 6 6 PRT Artificial Sequence Mimetope 6 Arg Ala Gly Asn His Ser 1 5 7 6 PRT Artificial Sequence Mimetope 7 Asp Pro Pro Gly Tyr Gly 1 5 8 6 PRT Artificial Sequence Mimetope 8 Arg Phe Gly Asn Asp Trp 1 5 9 4 PRT Artificial Sequence Mimetope 9 Arg Ser His Trp 1 10 6 PRT Artificial Sequence Mimetope 10 Asp Gln Met Gly Gly Gly 1 5 11 6 PRT Artificial Sequence Mimetope 11 Arg Ala Gly Ser Thr Trp 1 5 12 6 PRT Artificial Sequence Mimetope 12 Lys Gly Gly Leu Glu Ser 1 5 13 6 PRT Artificial Sequence Mimetope 13 Leu Pro Asn Leu Asp Thr 1 5 14 6 PRT Artificial Sequence Mimetope 14 Asn Arg Ser Gly Ser Trp 1 5 15 6 PRT Artificial Sequence Mimetope 15 Asp Val Ser Gly Gly His 1 5 16 6 PRT Artificial Sequence Mimetope 16 Leu His Ser Gly Gly Trp 1 5 17 6 PRT Artificial Sequence Mimetope 17 Ser Arg Ala Gly Gly Tyr 1 5 18 5 PRT Artificial Sequence Mimetope 18 Thr Ala Lys Met Asp 1 5 19 5 PRT Artificial Sequence Mimetope 19 Pro Thr Val Ser Met 1 5 20 5 PRT Artificial Sequence Mimetope 20 Arg Gln Ser Thr Met 1 5 21 5 PRT Artificial Sequence Mimetope 21 Gly Arg Thr Thr Met 1 5 22 5 PRT Artificial Sequence Mimetope 22 Ser Asp Gln Pro Leu 1 5 23 5 PRT Artificial Sequence Mimetope 23 His Thr Ala Ser Met 1 5 24 5 PRT Artificial Sequence Mimetope 24 Lys Ser Val Gly Leu 1 5 25 5 PRT Artificial Sequence Mimetope 25 Ala Asn Ile Ser Leu 1 5 26 5 PRT Artificial Sequence Mimetope 26 Pro Val Ala Pro Ile 1 5 27 5 PRT Artificial Sequence Mimetope 27 Arg Pro Thr Thr Leu 1 5 28 5 PRT Artificial Sequence Mimetope 28 Pro Asn Ala Asn Met 1 5 29 6 PRT Artificial Sequence Mimetope 29 Ala Thr Ser Phe Ala Pro 1 5 30 6 PRT Artificial Sequence Mimetope 30 Arg Arg Lys Gln Pro Thr 1 5 31 6 PRT Artificial Sequence Mimetope 31 Thr Ala His Val Ala Ser 1 5 32 6 PRT Artificial Sequence Mimetope 32 Thr Asn Lys Gln Pro Ser 1 5 33 6 PRT Artificial Sequence Mimetope 33 Lys Ser Tyr Thr Pro Glu 1 5 34 6 PRT Artificial Sequence Mimetope 34 Lys Trp Asn Tyr Thr Thr 1 5 35 6 PRT Artificial Sequence Mimetope 35 Gly Glu His Glu Ala Gly 1 5 36 6 PRT Artificial Sequence Mimetope 36 Glu Glu Asn Gly Arg Pro 1 5 37 6 PRT Artificial Sequence Mimetope 37 Gln Leu Gln Val Pro Pro 1 5 38 6 PRT Artificial Sequence Mimetope 38 Ala Pro Gly Asn Asp Gly 1 5 39 6 PRT Artificial Sequence Mimetope 39 Ala Gly Ala Thr Tyr Glu 1 5 40 4 PRT Artificial Sequence Mimetope 40 Met Asp Glu Arg 1 41 6 PRT Artificial Sequence Mimetope 41 Glu Arg Ser Gly His Trp 1 5 42 5 PRT Artificial Sequence Mimetope 42 Leu Ala Ser Gly Tyr 1 5 43 6 PRT Artificial Sequence Mimetope 43 Val Arg Ser Gly Pro Trp 1 5 44 6 PRT Artificial Sequence Mimetope 44 Arg Thr Ala Lys Val Ser 1 5 45 6 PRT Artificial Sequence Mimetope 45 Gln Lys Val Glu Pro Ser 1 5 46 6 PRT Artificial Sequence Mimetope 46 Thr Gly Val Tyr Pro Ser 1 5 47 6 PRT Artificial Sequence Mimetope 47 Gln Gly Pro Trp Ala Ser 1 5 48 6 PRT Artificial Sequence Mimetope 48 Ile Gly Asp Tyr Ser Lys 1 5 49 6 PRT Artificial Sequence Mimetope 49 Thr Gly Asn Gln Ala Thr 1 5 50 6 PRT Artificial Sequence Mimetope 50 Ser Asn Gly Glu His Ser 1 5 51 6 PRT Artificial Sequence Mimetope 51 Ser Gly His Glu Pro Thr 1 5 52 6 PRT Artificial Sequence Mimetope 52 Asp Ser Lys Glu Thr Ser 1 5 53 6 PRT Artificial Sequence Mimetope 53 Thr Ala Arg Trp Ala Asn 1 5 54 6 PRT Artificial Sequence Mimetope 54 Thr Ala Asn Glu His Thr 1 5 55 6 PRT Artificial Sequence Mimetope 55 Val Lys Ser Gly Val Ala 1 5 56 7 PRT Artificial Sequence Mimetope 56 Val Lys Ser Gly Asn Thr Trp 1 5 57 7 PRT Artificial Sequence Mimetope 57 Val Asp Arg Thr Lys Gly Trp 1 5 58 7 PRT Artificial Sequence Mimetope 58 Val Asp Gly Pro Asn Gly His 1 5 59 7 PRT Artificial Sequence Mimetope 59 His Pro Gln Asn Asp Asp Met 1 5 60 7 PRT Artificial Sequence Mimetope 60 His Pro Gln Asn Asp Asp Met 1 5 61 7 PRT Artificial Sequence Mimetope 61 His Pro Gln Asn Asp Asp Met 1 5 62 7 PRT Artificial Sequence Mimetope 62 His Pro Gln Gly Asp Asn Met 1 5 63 7 PRT Artificial Sequence Mimetope 63 His Pro Gln Gly Asp Ser Met 1 5 64 7 PRT Artificial Sequence Mimetope 64 His Pro Gln Asn Asp Asp Met 1 5 65 7 PRT Artificial Sequence Mimetope 65 Ser Asp Gly His Arg Leu Met 1 5 66 7 PRT Artificial Sequence Mimetope 66 Ser Asp Gly His Arg Leu Met 1 5 67 7 PRT Artificial Sequence Mimetope 67 Ser Asp Gly His Arg Leu Met 1 5 68 7 PRT Artificial Sequence Mimetope 68 Ser Asp Gly His Arg Leu Met 1 5 69 7 PRT Artificial Sequence Mimetope 69 Ser Asp Gly His Arg Leu Met 1 5 70 7 PRT Artificial Sequence Mimetope 70 Val Lys Gly Gly His Gly Ala 1 5 71 7 PRT Artificial Sequence Mimetope 71 Thr Pro Gly Ser Leu Gln Met 1 5 72 7 PRT Artificial Sequence Mimetope 72 Ser Ala His Gln Asp Tyr Ile 1 5 73 7 PRT Artificial Sequence Mimetope 73 Thr Pro Gly Ser Leu Gln Met 1 5 74 7 PRT Artificial Sequence Mimetope 74 Thr Pro Gly Ser Leu Gln Met 1 5 75 7 PRT Artificial Sequence Mimetope 75 Thr Pro Gly Ser Leu Gln Met 1 5 76 7 PRT Artificial Sequence Mimetope 76 Asp Gly Ser Arg Ile Gln Met 1 5 77 7 PRT Artificial Sequence Mimetope 77 Asp Gly Ser Arg Ile Gln Met 1 5 78 7 PRT Artificial Sequence Mimetope 78 Asp Gly Ser Arg Ile Gln Met 1 5 

What is claimed:
 1. A chimeric β-lactamase enzyme comprising β-lactamase and a mimetope inserted into or inserted by replacing at least one amino acid thereof, wherein said chimeric β-lactamase has an enzymatic activity which is modulated upon the binding of a binding molecule to said mimetope.
 2. A chimeric β-lactamase as recited in claim 1 wherein the binding molecule binds to an active conformation of the chimeric β-lactamase.
 3. A chimeric β-lactamase as recited in claim 1, wherein the binding molecule binds to an inactive conformation of the chimeric β-lactamases.
 4. A chimeric β-lactamase as recited in claim 1, wherein the binding molecule is an antibody.
 5. A chimeric β-lactamase as recited in claim 1, wherein the conformation of the chimeric β-lactamase is shifted from an active form to an inactive form upon binding of the binding molecule to the chimeric β-lactamase.
 6. A chimeric β-lactamase as recited in claim 1, wherein the enzymatic activity of the chimeric β-lactamase is inactivated upon binding of the binding molecule to the chimeric β-lactamase.
 7. A chimeric β-lactamase as recited in claim 1, wherein the enzymatic activity of the chimeric β-lactamase is activated upon binding of the binding molecule to the chimeric β-lactamase.
 8. A chimeric β-lactamase as recited in claim 1, wherein the sequence of the mimetope is inserted into a sequence of β-lactamase which is remote from the active site thereof.
 9. A chimeric β-lactamase as recited in claim 1, wherein the mimetope comprises 10 or less amino acids.
 10. A chimeric β-lactamase as recited in claim 1, wherein the mimetope is a random peptides sequence.
 11. A chimeric β-lactamase as recited in claim 1, wherein the mimetope is any one of a sequence identified from SEQ ID Nos. 1-78.
 12. A chimeric β-lactamase enzyme comprising β-lactamase and an antigenic mimetope inserted into or inserted by replacing at least one amino acid thereof, wherein said chimeric β-lactamase has an enzymatic activity being modulated upon the binding of an antibody to said antigenic mimetope. 